1. Field
The present invention relates to a fall arrest system energy absorber and safety device and in particular to a device including an energy absorber arrangement to absorb the energy of a fall arrest event.
2. Related Art
Fall arrest systems are used to prevent personnel working at height from suffering injury as a result of falling. Fall arrest systems are often referred to as height safety systems or fall prevention systems. Frequently such systems utilise an energy absorber device arranged to be activated if a load above a predetermined threshold is applied. The energy absorber devices can take many forms such as fabric rip devices, friction brake devices or plastically deformable arrangements that are plastically deformed during deployment in order to absorb energy.
One type of device that relies on an energy absorber is a so called safety block arranged to be suspended overhead from an anchor structure. Such arrangements typically include a drum upon which a safety line is wound; a speed responsive mechanism arranged to inhibit the drum rotation above a predetermined rotational speed and an energy absorber device arranged to be deployed if a load above a predetermined threshold is encountered when the speed responsive mechanism is deployed. Exemplary arrangements are disclosed in WO2009/047541 and WO2008/007119.
Another species of fall arrest or fall safety device is shown in for example WO95/01815, which discloses a device for use with a lanyard, and includes an energy absorber, and is used to connect between a user's harness and an anchor point for the lanyard.
Another type of fall arrest or fall safety device is an energy absorbing anchor post such as the arrangement shown in EP1282460. The system is, for example, suitable for use in cable based fall arrest systems anchored to structures such as roofs. The cable needs to be held well clear of the roof surface to permit fall arrest system travellers to travel un-impeded along the cable. The casing of the post enables this to be achieved. A coiled plastically deformable energy absorber is disclosed in EP1282460.
An example of a further alternative embodiment of safety device for a fall protection system is shown in EP0605538. The system is, for example, suitable for use in a safety line system to absorb sudden impact loadings and absorb impulse or shock energy. The system utilises an energy absorber device as does the previous examples but in this instance absorbs energy as two components move translationally or linearly relative to one another rather than rotationally as in the previously described prior art examples. In the primary described embodiment in EP0605538 movement of a rod causes a retaining nut to be forced along a sleeve to permanently outwardly plastically deform the sleeve. The plastic deformation of the sleeve absorbs the energy.
An improved arrangement has now been devised.